FIGURE 1.

Functional assessment of membrane integrity in bacteria undergoing the WH1(A31V)-mCh amyloidosis. (A) Images overlaying red epifluorescence and DIC micrographs of E. coli MDS42 cells (left), or the same strain expressing (2.5 h post-induction) mCherry (center), or WH1(A31V)-mCh (right). Arrows: bacterial cells having lost turgor. (B) Left: Estimation of the ATP levels in whole cell bacterial lysates. Mean values (bars) and SDs (whiskers) from 3 biological replicas are displayed, normalized to the values measured for prionoid-freed cells. Right: Effect of the expression of WH1(A31V)-mCh on the luminiscence of live E. coli cells that constitutively expressed bacterial luciferase. The levels of the prionoid were monitored in parallel by measuring the red fluorescence emission (inset). Dots: mean values from three independent culture wells; whiskers: SDs. (C) Intracellular iron levels in naïve bacteria or upon expression of WH1(A31V)-mCh. Iron uptake is impaired in E. coli cells undergoing amyloidosis. Y axes represent the read-out of the ferrozine assay (light absorption at 562 nm; left) and its conversion to the amount of ferrous iron (right), both expressed per mg of dry cell mass. Data from 6 biological replicas. One-way ANOVA statistical significance analysis, followed by Tukey’s pairwise difference test, was performed for panels B and C. ^∗∗p < 0.01; ^∗∗∗p < 0.001.